Chaos Corona Forum

Chaos Corona for Cinema 4D => [C4D] Bug Reporting => Topic started by: sirio76 on 2020-04-16, 12:55:34

Title: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-16, 12:55:34
Is this the expected behavior??
Specular highlight vary wildly depending on the size of the render/distance from camera, seems also related to MIP mapping. It happens on both preview and real scene.

Title: Re: Yet another critical problem with bump mapping
Post by: maru on 2020-04-16, 13:36:14
I think this one would be the same in 3ds Max. It's just how things work.
Title: Re: Yet another critical problem with bump mapping
Post by: Nejc Kilar on 2020-04-16, 13:53:44
I think this one would be the same in 3ds Max. It's just how things work.

Em, its just how things work in Corona or in real life as well? :)

Thanks for reporting, sirio76!
Title: Re: Yet another critical problem with bump mapping
Post by: maru on 2020-04-16, 14:25:46
I think this one would be the same in 3ds Max. It's just how things work.

Em, its just how things work in Corona or in real life as well? :)


In Corona/Max/C4D/other, anywhere where there is texture filtering involved. But of course a dev's opinion would be more relevant here.
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-16, 14:27:18
It's just how things work.
Not in real life ;) I'm building all my shaders using physical samples of material inside a real calibrated setup and a 3D equivalent scene, also calibrated using correct exposure and light intensity. Results are mostly close to real life(below just a couple examples) but when I use a material with strong bump, results are inconsistent. Simply take several shots of a leather at different distance, the highlights is consistent no matter how you look at it, in Corona is just wrong and it's worrisome that you do not consider this a critical issue. It needs to be investigated and fixed. Sorry for the rant but I'm investing time and resources in Corona and I want things to work properly ;)
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-16, 14:38:32
Also, it's not the same with Cinema materials, no matter if I use MIP or other sampling methods. I do not have Vray installed anymore but I'm pretty sure it doesn't have this problem neither and to be honest in over 20 years of work in CG using tons of other engine I do not remember this behavior.


Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-16, 19:09:52
@maru or any other developers, have you seen that?
Title: Re: Yet another critical problem with bump mapping
Post by: Fluss on 2020-04-16, 19:49:14
Wouldn't bump to roughness solve those sampling issues?
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-16, 23:06:20
Wouldn't bump to roughness solve those sampling issues?

I don't know about this feature, can you elaborate?
Title: Re: Yet another critical problem with bump mapping
Post by: maru on 2020-04-17, 12:17:45
Here is a reply from our dev team:

Quote
This issue is present in all renderers which perform texture filtering / mip-mapping and it needs special handling - here is a paper from Pixar which explains this well: https://graphics.pixar.com/library/BumpRoughness/paper.pdf

We may, however, look into this - so stay tuned!

Also, please note: I am not a developer. :)
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-17, 13:20:14
Thank a lot for looking into this, I really appreciate your support:)
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-17, 13:25:38
In the mean while I've founded a combination of maps/parameters that works fairly well, but it took me a lot of effort because of the filtering issue and close-up still look different:


Title: Re: Yet another critical problem with bump mapping
Post by: Redeemer on 2020-04-19, 11:24:27
Posted in 'I need help' but I guess it is the same bug as Sirio pointed out:
https://forum.corona-renderer.com/index.php?topic=28892.0 (https://forum.corona-renderer.com/index.php?topic=28892.0)

Title: Re: Yet another critical problem with bump mapping
Post by: Fluss on 2020-04-19, 12:09:30
Here is a reply from our dev team:

Quote
This issue is present in all renderers which perform texture filtering / mip-mapping and it needs special handling - here is a paper from Pixar which explains this well: https://graphics.pixar.com/library/BumpRoughness/paper.pdf

We may, however, look into this - so stay tuned!

Also, please note: I am not a developer. :)

Great, I'm so happy to hear that you're considering to solve this!
Title: Re: Yet another critical problem with bump mapping
Post by: Nejc Kilar on 2020-04-20, 08:51:36
I'd just like to point out that this report could potentially be about the same bug that I'm seeing here - https://forum.corona-renderer.com/index.php?topic=28382.0 :)
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-20, 11:10:45
Please anyone with similar issues report it to developers, the more we are the more likely it will be fixed.
Title: Re: Yet another critical problem with bump mapping
Post by: agentdark45 on 2020-04-20, 15:33:23
Max Corona user here and I can confirm (along with others) that there's a big issue with bump mapping being view/resolution dependant. The issue becomes more apparent when using micro fine bump maps (fine plastic pitting, fine stainless steel brushing e.t.c).

I've posted this before but if you want an example of rock solid bump/filtering implementation, at least as far as needed for our purposes take a look at this video:


The anistropy of the stainless steel is purely derived from the fine bump map (no dedicated anistropy slot) and being a dual user of Corona and Fstorm I can guarantee that if you try this in Corona using bump maps, it will break. You might get a semi decent result for one particular view but as soon as you increase the render resolution or change the view all hell breaks loose and you'll have to re-tweak the material.

This is quite a large problem imo, as it impacts pretty much all common materials - wood, concrete and wall paint for example. The natural anistropy from the video example will be lost on common materials unless explicitly mapping it (and even then you won't be able to get as fine a result unless rendering larger and downsampling).

This isn't a knock on Corona - I still use it for 95% of commercial projects, I'm just trying to aid in key areas that could use some improvement.
Title: Re: Yet another critical problem with bump mapping
Post by: sirio76 on 2020-04-20, 16:20:23
This is quite a large problem imo, as it impacts pretty much all common materials

+1
I can't see how such an important feature has been neglected until now. An implementation like Fstorm would be ideal but I would be more than happy even if they simply solve the bug reported here. This is not a fancy new feature needed by a very few users, it is really a basic needs for all of us and it's crucial to get consistent shaders.
Title: Re: Yet another critical problem with bump mapping
Post by: Designerman77 on 2020-04-20, 17:09:42
Also immediately noticeable: nice tone mapping, color grading & natural looking light dynamics in FStorm...

I'm sure Corona devs are working on getting there. :)
Title: Re: Yet another critical problem with bump mapping
Post by: lupaz on 2020-04-20, 23:15:19
+1 about the bump mapping. (I'm a Max user though)